Tool for truing crankshafts and the like



Nov. 18, 1958 G. w. DAvlr-:s 2,860,539

TOOL FOR TRUING CRANKSHAFTS AND THE LIKE Filed Sept. 8, 1955 i Il lr g 'i 23 'I l', d ,l s l 17 L 13"" t l14 j; f5 I2 40 @www 4 T TOR/VE Y *naar f" United States Patent (Dtice 2,860,539 Patented Nov. 18, 1958 TOOL FOR TRUING CRANKSHAFTS AND THE LIKE Gomer William Davies, Gainesville, Fla.

Application September 8, 1953, Serial No. 378,776

1 Claim. (Cl. 82-4) The present invention relates to the art of cutting or turning tools for shaping generally cylindrical shafts, and particularly concerns tools for truing crankshafts of internal combustion engines as well as other types of engines.

An important object of the invention is to provide a tool adapted for truing to a cylindrical form of predetermined diameter, a portion of a crankshaft of an engine such as an internal combustion engine without the necessity of removing the crankshaft from the engine to per form the cutting operation, although if desired the tool may also be used on a crankshaft disconnected from an engine and mounted in a lathe or the like.

A further object of the invention is to provide an improved cutting tool including a resiliently mounted member adapted to accommodate the tool to crankshafts of irregular shapes.

Another object of the invention is to provide a cutting tool including a resilient assembly on a shaft being worked on, the pressure between the cutter and the shaft being adjustable, to prevent chattering or binding of the tool during the cutting operation and improving the accuracy and ease of cutting.

A further object is to provide a truing tool having a lesser number of parts and simpler structure than conventional tools while affording a cutting action of increased efficiency.

The present invention provides a tool of the character described adjustable to accommodate shafts of various diameters and adaptable to turn shafts down to true cylindrical form with the length of the cylindrical form limited only Iby the length of the cutter. The invention is not limited in its application to truing, turning and cutting cranksha'fts since it is adapted to handle cylin* drical shafts of other types. Y

Other and further objects and advantages of the invention will become readily apparent from the following description and drawing, wherein:

Fig. l is an elevational View of a preferred embodiment of the invention with a portion cut away to show internal construction.

Fig. 2 is a sectional view taken on lines 2-2 of Fig. 1.

Fig. 3 is a sectional view taken on lines 3-3 of Fig. 1.

In Figs. l, 2 and 3, the tool body 10 is a generally at cylindrical structure having a portion cut out to form a modified rectangular throat or opening 11 with upper inwardly tapering sides 12, 13. The stationary keeper plates 14, 15 iit into slots or channels in the inclined sides 12, 13 and are arranged to bear tangentially upon a shaft S to be cut or turned to a true cylindrical form while the shaft is supported in the body with its axis substantially coinciding with that of body 1G. A slot 16 is provided in the body to hold a cutter 17. As shown in Figs. 2 and 3, the cutter 17 is entered into the body 10 laterally. The slot 16 is so disposed that the cutting tip or edge 18 of the cutter lies on a diameter of the circular body 10 and a coinciding diameter of the shaft S to be turned. The position of the cutting edge 18 and the positions of the points of tangency of the keeper platesl 14, 15 with shaft S determine the radius of curvature of the cylindrical surface to which the shaft will be cut during operation of the tool. substantially radially into body 10 serve to position the cutter 17 a desired distance into the throat 11. This feature allows adjustment of the depth of cut. At least one screw 21 is threaded in a chordally disposed threaded bore 22 and bears on cutter 17 to hold it in cutting position in slot 16. If desired a plurality of such screws in parallel bores may Abe provided to hold the cutter more rigidly in cutting position. A plurality 0f lbore holes or sockets 23 are radially disposed in body 10. Suitable bars or handles (not shown) may be mounted inv these sockets for rotating the tool during operation thereof.

A special feature of the invention is the arrangement of the removable members in throat 11. A pair of keeper plates 24, 25 of hardened tool steel or the like are carried in channels of a rocker on bridge plate 26. Plates 24, 25 are arranged to bear tangentially on the shaft S to be worked upon. In order to compensate for irregularities in the shape of the shaft and to insure that the keeper plates 14, 15 remain rmly in contact with shaft S, the bridge plate 26 is spring loaded in a floating mounting. The springs 27, 28 t into bore holes 30, 31 in the base plate 29. The bridge plate 26 is generally U-shaped in cross section as shown clearly in Fig. 2, with side portions 32, 33 curved conveXedly at their lower ends and straddling the block or lbase plate 29. Base plate 29 is correspondingly curved concavely at its upper side 34. The bridge plate 26 and base plate 29 are spaced apart a short distance so that the ibridge plate is movable under spring pressure in response to irregularities encountered by the keeper plates 24, 25 and the cutting edge 18 as the tool is rotated around shaft S during the cutting operation. A pin 35 passes through holes in the sides 32, 33 of the bridge plate and through base plate 29. The hole 36 in base plate 29 is elongated while the holes in the bridge plate sides are circular and equal in diameter to pin 35. By this arrangement of the pin and holes the movement of the bridge plate 26 is guided substantially diametrally while the curvature and spacing of the plates permits a rocking movement of the bridge plate.

A pair of slots or channels 37, 38 are cut in `body 10 into which fits the removable bridge or base'bar 39. A

screw 40 is threaded into bar 39 and contacts bearing plate 41 mounted in the bottom of base plate 29. By v adjusting screw 40, the pressure of keeper plates 24, 25 on shaft S is regulated and correspondingly the pressure of cutting edge 1S on the shaft S may be regulated. This pressure may be set at any desired amount while keeper plates 24, 25 will still be movably disposed with respect to both base bar 39 and shaft S. This floating mounting of the keeper plates 24, 25 is very important in the present invention and serves to eliminate chattering and binding during rotation of the tool while improving the accuracy and efficiency of the cutting operation.

ln operation the tool members in the lower portion of the throat, 11 are removed and the body member 10 is placed on the shaft to be trued to cylindrical form with the shaft contacting stationary keeper plates 14, 15. It will not be necessary to remove the shaft from an associated engine to mount the tool, since merely disconnecting the usual piston from the point of the shaft to betrued will usually furnish suicient clearance to mount and operate the tool. After mounting the tool body cutter 17 should be positioned for the desired depth of cut. If desired and to obtain increased accuracy cutter 17 can be positioned before the body is mounted on the shaft S. The depth of cut is determined by adjusting screws 19, 20 and then tightening the screw or screws 21. Bridge Screws 19 and 20 threaded 3. plate 26 may normally be kept assembled with base plate 29,. with the springs 27, 28 therebetween and held in place by pin 35. The plate assembly is then placed in throat 11 with keeper plates 24, 25 in contact with shaft S. Bar 39. is inserted in channels 37, 38 and screw 40 is tightened to adjust the pressure on cutter edge 1S and keeper plates 14, 1S. It must be emphasized at this point that the pres.- sure .On the cutter and keeper plates is transmitted via springs 27, 28 so that as irregularities in the shape of the shaft occur at the cutter or keeper plates, the tool does not `bind but continues to rotate as the bridge platek 26 moves in response to the degree of irregularity encountered. Suitable bars or handles are inserted in sockets 23 and the tool isk manually rotated until shaft S is turned down tothe desired cylindrical shape. When the shaft is turned down to predetermined size the cutter can be progressively advanced to reduce further the radius of curvature of the shaft. The length of cut will of course depend on the length of cutter edge 18. The tool is adapted to hold cutters of various lengths as required, and cutters may be replaced at will without demounting the tool from shaft S. The tool as thus mounted on shaft S is operable invery close quarters since the operating 'bars may be inserted intro any exposed socket 23. It will be noted that the tool is arranged so that all bearing surfaces may be formed of hardened tool steel inserts or plates while the Abody of the tool may be formed as a casting, forging, or the like of other suitable metal.

From the foregoing description it is apparent that there has been provided an improved cutting or turning tool which is responsive to irregularities in the shape of the shaft being turned while the pressure on the cutting edge and associated keeper plates is maintained at a predetermined amount. This pressure is adjustable within predetermined limits and with an adjusting screw 40 of very fine pitch the pressure can be adjusted uniformly in a very tine increment as desired.

Although a single embodiment and a limited number of'modiiications of the invention have been dsecribed it will be obvious to those skilled in the art that many changes and equivalent structures are possible. It is therefore desired that the invention be limited only by the scope of the following claim.

I claim:

A tool for truing shafts and the like, comprising a generally U-shaped housing having an arcuate outer perimeter, said U-shaped housing having a yoke and a pair of arms which are joined by said yoke and occupy a common plane therewith, said arcuate Perimeter extending, substantially, from the free end of one of saidv arms around said yoke to the free end of the other arm, a slot formed in said yoke, a cutter adjustably mounted in said slot, a pair of bearing plates secured to said housing on opposite sides of said cutter, a bridge extending between the arms of said U-shaped housing, adjacent their free ends, a block slidably mounted between said arms for longitudinal movement along said arms in one direction toward said bridge and in the opposite direction toward the yoke of said housing, an adjusting screw on the bridge engaging said slidable block to urgeV said block in the direction of the yoke of said housing, a rocker slidably mounted on said block for slidable movement relative to said block in one direction toward the bridge and in the opposite direction toward said yoke, said rocker being also mounted on said block for rocking movement relative thereto in the plane occupied by said yoke and said arms, a pair of compression springs mounted between said block and said rocker on opposite sides of the rocking axis urging the rocker in the direction of said yoke, a pair o'f bearing plates mounted on said rocker opposite the lbearing plates on the housing, said bearing plates on the rocker being spaced from the bearing plates and cutter on the housing to provide room for a shaft placed between said bearing plates on therocker and said bearing plates and cutter on the housing, whereby the adv justing screw on the bridge may be turned to push the block and said spring-urged rocker in the direction of the yoke of the housing, thereby pressing the shaft by means of said bearing plates on the rocker against said bearing plates and lcutter on the housing, and means for turning said housing about the axis of said shaft t0 cause the cutter to true said shaft.

References Cited in the iile of this patent UNITED STATES PATENTS 270,474 Plummer Jan. 9, 1883 640,751 Corwin Ian. 9, 1900 1,235,914 Murrie Aug. 7, 1917 1,491,847 Creed Apr. 29, 1924 1,516,509. Smith Nov. 25, 1924 1,971,280 Spencer Aug. 21, 19.34 2,109,371 Groene Feb. 22, 1938 2,148,329 Tindall et al. Feb. 21, 1939 2,219,245 Zitzerman Oct. 22, 1940 2,322,623 Floeter June 22, 1943 2,453,797 Johnson Nov. 1,6, 1948 2,531,160 Rutherford Nov. 21, 195.0

FOREIGN PATENTS 244,690 Great Britain Dec. 24, 19,125. 

